The invention relates to a device for finishing at least one lengthwise edge of a sheet of material, which at least on this lengthwise edge has a lengthwise strip of material which is less thick than the remainder of the sheet of material, including a plurality of finishing units arranged one after the other in the direction of conveyance of the sheet of material, on a common support, and this support can be adjusted transversely to the sheet of material by a drive motor, which can be controlled by a scanning system which monitors the edge of the sheet of material before the finishing units and is connected with the support, so that the finishing units follow deviations in the side of the sheet of material.
A device of this sort is known from German DE-OS No. 30 47 693. The two parallel edges of a sheet of material are finished by using this device. Several finishing units are associated with each edge of the sheet of material, of which the setting is controlled transverse to the sheet of material by a single scanning device. These scanning devices have optical barriers scanning the lengthwise edges of the sheet of material. If the illumination of the photoelectric elements by these optical barriers is interrupted, showing that the lengthwise edge of the sheet of material has moved to the side, then the drive motor for the transverse setting of the finishing unit is shifted so that, by following the optical barrier, its photoelectric element is illuminated again. The finishing unit (e.g., including a hemmer and a sewing machine) likewise follows the deviation of the lengthwise edge of the sheet of material, so that the finishing can be continued. This known device can work satisfactorily when sheets of material with the two perfectly straight parallel lengthwise edges are to be treated.
However, if the sheets of material have curved lengthwise edges and do not run parallel and still have not been trimmed, and furthermore have lengthwise strips of material on their lengthwise edges that are thinner than the remainder of the sheet of material, then the finishing could damage the sheet or the installation itself during the operation. With a curved lengthwise edge of the sheet of material, even optical barriers connected tightly with the support for the finishing unit which can be set transversely move correspondingly to the side, which results in a correspondingly uneven or curved finishing (hemming and sewing) of the lengthwise edge, and the lengthwise edge which is so treated is not parallel to the adjacent lengthwise edge (e.g., nap-edge) of the sheet of material which is to the side of and bordering the different material thicknesses. A sheet of material which is so treated yields a defective product.